In vitro and in vivo (experimental mouse infections) trophozoites of Naegleria gruberi, subjected to various cytochemical staining procedures (acid phosphatase, B-glucuronidase, aryl sulfatase) will be studied by EM to ascertain origin and method of elaboration of lysosomal products in tissue. Lysosomal products from polymorphonuclear leukocytes in in vivo situation will also be studied to determine their role in overwhelming autolysis. Entamoeba histolytica in vivo surface phenomena are being studied by EM fo elaboration of various mechanisms for secretion of lytic enzymes.